won't stay closed
 

My SBT opens up when fired it locks up tight with no play but opens up when shot??

Parker SBT SC grade

It is usually a bolt bite issue. Or a weak/broken top lever spring. But usually the bolt.

thanks I'll contact previous owner and find out as much as I can about previous work etc

forgot to ask what is the bolt bite

My SC does that on occasion with 3 dram 1 1/8 oz loads. My shoulder can’t stand a steady diet of 3 dram shells so I am delaying getting it fixed. I load very light 3/4 or 7/8 oz. Loads and never have an issue. Score is not a big issue with me but comfort and pain is.

I assume an SBT "wear plate" is something along the same lines as the locking plate in something like a 101, Citori etc. and not shaped like the locking block in my Perazzi's?

Parker bolting from a 1930 catalog.

Attachment 123736

The fit of the replaceable "bolt plate" is critical as well as the strength of the top-lever spring.

This may sound crazy, Grant, but my 1929 SC opens after every round when shooting Winchester 1145fps #8 shells BUT NEVER opens using Remington 1145 or 1100 #8 shells and never opened using RST shells when they were available. I have no idea why and shoot the Remington shells exclusively. I do not "snap" the gun shut - I release the lever before closing it tight. Good luck - these are great guns!

Do you put grease on the wear plate?

Sorry for the late reply.......no, I don't grease any internal parts but clean the gun regularly...sorry again!

My understanding from Chris Dawe at Stillwater Restorations is that this is a pressure issue. Higher pressure ammo. I get the same thing shooting 1 1/8oz/1255fps Winchester Super X field loads through my Ithaca NID4E yet I can put Eley Bismuth loads of 1 1/4oz 1250 fps loads through without issue. Chris advised me to not to continue shooting loads with higher pressures and to search for or reload low pressure loads or risk eventually putting the gun off face. I heeded his advice after 5 rounds and have been running low presdure 1oz loads ever since w/o a hitch.

I’ve had this same problem with an Ithaca Flues SBT, an Iver Johnson Specialty Trap and a Fox SBT. In all three cases the issue was with the locking bolt.